Didn't get a t-shirt; didn't even get the code to pass -c but didn't get any useful info by adding strict, warnings, diagnostics, etc. ad nauseum.

Proofread... repeatedly. To no avail. (Remember: the one-eyed man is king in a world of the blind)

Lo and behold: your wiki ref led me eventually to a Stevenson site where I found this:

13. Hey, the perl script doesn't work! What's the deal?

The production people at the publisher tried valiantly to get the perl script typeset without any errors, but one error did slip in. It is located on the eighth line. Where the book says$o=~s/.chr((and so on, it SHOULD say$o=~s/./chr((
and so on.